System for reducing the emission of unburned combustibles from an internal combustion engine



J. DOLZA July 6, 1965 3,192,706 SYSTEM FOR REDUCING THE EMISSION OF UNBURNED COMBUSTIBLES FROM AN INTERNAL COMBUSTION ENGINE 3 Sheets-Sheet 1 Filed 001'.. 26, 1962 /IV (A750 MEA/V EFFE MIX 7' URE IN INVENToR. J/f/v a/.ZA

July 6, 1965 J. DoLzA 3,192,706

SYSTEM FOR REDUCING THE EMISSION OF UNBURNED COMBUSTIBLES FROM AN INTERNAL COMBUSTION ENGINE Filed Oct. 26, 1962 5 Sheets-Sheet 2 A/x? F2044 26 CLEANER /fa T INV EN TOR. 7d///v ozzn July 6, 1965 J. DoLzA 3,192,706

SYSTEM FOR REDUCING THE EMISSION OF UNBURNED COMBUSTIBLES FROM AN INTERNAL COMBUSTION ENGINE Filed Oct. 26, 1962 3 Sheets-Sheet 3 INVENToR. Jf//V aLz/r United States Patent O pal aisance SYSTEM EGR REDUCING THE EMISSIN GF UN- Y BUE-NED CGMBUSTEELES FROM AN INTERNAL CMBUSIION ENGINE Y .lohn Dolan, 8l() State St., Fenton, Mich. Filed (let. 26, 1962, Ser. No. 233,333 le Ciaims. (Ci. dil-Sli) sion of unburned fuel components is traceable to the fact that each cylinder combustion chamber is functioning so ineciently as to not properly support combustion at a level compatible with relatively complete combustion of the fuel being supplied to the chamber.

In the present invention, it is recognized that if under coasting, idling, or iight load operation only some of the cylinders are kept active to maintain the engine operative while the remainder are inactivated, then more efcient engine operation is realized accompanied by more cornplete combustion of the fuel and less emission of unburned combustibles to the atmosphere.

To practice the subject invention, it is necessary that the engine be split relative to the supplying of a combustible mixture to the engines cylinders. More specifically, this is achieved by providing at least-two carbureting systems each supplying half of the engines cylinders. Further, in the present invention means is uniquely provided for rendering inoperative one of the carburetion systems and the associated ignition Vsystem for half cylinders under conditions when relatively high power outputs are unnecessary.

The present split engine mechanism includes what may be termed active and inactive carbureting systems and cylinders. Under normal or high speed operation both the inactive and :active carburetion systems are functioning to provide the appropriate fuel-air ratio to each of theirvcylinder groups. On the other hand, under conditions where split engine operation is both desirable and feasible, only the active carburetion system is Yoperative with its associated cylinders to provide all of the power necessary to keep the engine running. Under these conditions, the remaining or inactive cylinders are merely floating in the system neither creating nor absorbing power. In this way the active cylinders are functioning efficiently to consume substantially all of the fuel supplied thereto and, at .any rate, emitting unburned combustibles at a level equal to or below the standards set by statute in many states.

In order to reduce the pumping losses which would otherwise obtain in deactivating hall:` of the engine cylinders a unique mechanism is provided forbypassing the inactive carburetion system in such a manner that upon the demand for full engine operation, fuel and air ow may be resumed through the inactive carburetion system in a way to smoothly restore normal engine operation.

The details, as well as further objects and advantages, of the present inventionwill be apparent upon a perusal of the detailed description which follows as Well as by reference to the drawings. 1

In the drawings: D

FIGURE 1 is a graphic representation of the emission problem created by ineicient engine operation as ICC well las the improvement effected by the present invent-ion;

FIGURE 2 is a diagrammatic representation of an internal combustion engine embodying the subject invention;

FGURE 3 is a more complete diagrammatic engine fuel control system embodying the subject invention;

FlGURE 4 is a graph showing the improved results obtained with the modification of FIGURE 5 FIGURE 5 is a modification embodying an improved arrangement for burning unburned combustibles in the exhaust during split engine operation.

It has been observed by test work on automotive-type engines that by increasing the percent of work generated by a cylinder, or the percent of Indicated Mean Effective Pressure (hereinafter called IMEP) from engine idle (or coasting condition) Ito approximately 30% of wide open throttle, IMEP, the content of CO and hydrocarbons all decrease as may be seen in referring to FIGURE l.

In fact, while an engine is coasting the IMEI is at its lowest value, being negative when no firing takes place `and positive only when intermittent firing occurs. It is to be understood that coasting is the condition in which the engine throttle is closed while the car is traveling with the engine still coupled to the drive shaft and in which condition the momentum of the car keeps the engine running at speeds greater than idle.

When the throttle of an engine is closed immediately after wide open throttle operation, the intake manifold may be coated to a very great extent with liquid gasoline with the manifold walls actually covered with a large number of fuel droplets. The closing of the throttle reduces the amount ofl air pressure facilitating the evaporation of the liquid fuel and, because of the velocity that the fuel particles have in the direction of the previous air flow inthe manifold, some of these drops keep moving into'the engineV cylinders. vThe resultant fuel-air mixture flowing intoV at least some of the cylinders will be too rich to ignite during some of the initial coasting periods. Gradually the mixture will lean down to approximately idle strength IM, as seen in FIGURE 1. However, tiring may still be intermittent since the amount of fuel-air mixture entering a cylinder may be too little due to dilution by the residual exhaust in the combustion chamber to support combustion. This missing or failure of the ,cylinder to fire will actas a scavenging cyclerso that the following suction stroke will add sufficient mixture to the cylinder to permit ring to take place. For this reason, again referring to FIGURE 1, coasting is shown as taking place with: (A.) negative torque and negative IMEP and very high hydrocarbons since fuel may not burn when the engine is not tiring, and (B) a low positive percent IME?, usually lower than engine idle because the amount of charge per cylinder may be less than at idle, at the same time, there is high hydrocarbon and CO emission since'the fuel-air ratio introduced into the cylinder is richer thanstoichiometric (that combination of fuel and air to achieve complete combustion).

At idle, the IMEP is high enough to balance the internal and external frictions of the power plant. If the idle is properly set, firing taires place every time the mixture is ignited at the end of the compression stroke, but combustion is not completed because the mixture necessary Y for consistent tiring is above the stoichiometric value. The

result is that CO and hydrocarbons are present in the exhaust of the engine land are thus dischargedinto -the atmosphere in quantities above that deemed lto betolerable yparticularly in city environments.

'Again referring to FIGURE 1, the vertical line marked idle IMEI consequently intersects both the f/a line, free essere The next vertical line to the right of idle is designated IMEP of one-half of the cylinders working when the other half are owing or pumping air. This type of operation is best understood by referring to the schematic representation of FIGURE 2. Inthis case, an engine is indicated generally at 1Q and includes an active cylinder 12 and an inactive cylinder 14 pistons 15 and 17 of which are suitably articulated through a connecting rod system indicated generally at 16 to a commonV crankshaft 18. Active cylinder 12 is supplied with a fuel-air mixture through a carburetor device indicated generally at 26 which includes a throttle valve 22. The combustible mixture is admitted to the combustion chamber of cylinder 1,2 through inlet valve 24 where itis ignited by a spark plug 26 after which the combusted materialsare exhausted through exhaust valve y23 and exhaust passage 30. Generally the same components are provided for the inactive cylinder 14, however for illustrated purposes, the carburetion mechanism is not shown in intake passage 32 of the inactive cylinder since, in the illustration, the inactive cylinder is simplyrpurmping air. l n

In the .left hand side of the engine, active cylinder piston 1.5 is pumping'a combustible mixture through carburetor 2 9 whose throttle 22l is set to idle high enough so that it may generate suicient power to drag the right hand or inactive piston 17 and perform a substantially adiabatic compression in drawing a full charge of air, compressing it and permitting it'to expand. Thus the right handrcylinder 14 acts as intermittent energy storing system since during the' compression stroke it draws energy from the tiring cylinder and returns it during the ,expansion stroke. s

The diagram of FIGURE l shows that because of this higher percent IMEP required from the firing cylinders, the f/a point IIM, the hydrocarbon point IIE and the CO point IIC are considerably lower than the corresponding values IM, `IE and IC at engine idling when all of the cylinders are tiring. Y

When an engine idles with some of its cylinders pumpingvair without the very large depression caused by the throttle associated therewith, it hasV to Yovercome considerably less pumping loss. Thus, the amount of Work performed by the tiring cylinders to keep the engine idling is less than when all of the cylinders lare ring at idle. Wheny half the cylinders are .tiring they work at higher thermal and combustion eciencies which increases engine economy and drastically reduces the emission of unburned hydrocarbons and CO. In other words, the net result is that an engine idling on half of the cylinders and pumping unrestricted air with the remaining cylinders uses considerably less fuel than the engine idling by tiring all cylinders. If we use the following symbols:

W1/2=weight of air consumed by the Vtiring cylinders when engine is idling with 1/2 of the cylinders WA=weight of air consumed by the engine when idling by ring all cylinders IIEXWUZ is the weight of hydrocarbon with 1/2 of cyllinders firing and 1/2 cylinderspumping IICX W1 /2 weight of CO with half of cylinders tiring and I half of `cylinders pumping IEXWA weight Yof hydrocarbons on conventional idle ICX Wg, weight of CO on conventional idle Equations A and B state that the overall weight of hydrocarbons and CO exhausted by an engine with only l 1/2 of its cylinders firing at idle or olf idle, is less than the reduction one would expect froml the percent of hydrocarbon and CO in the exhaust of the operaitng portion of the engine.

In FIGURE 1, the percent of CO presently allowed by those citiesror states having antipollution laws is indicated with SC and a horizontal line at that value shows that a conventional engine when coasting generates a percent of CO indicated by 1'() and at idle a percent indicated by IC where Similarly the percent of hydrocarbonscoasting IE and idling IE are related to the amount SE allowed by statute by the expression Test results show that .the percent of hydrocarbons IIE at the exhaust of the `operating half of the engine can be controlled, to approximately the permissible value SE. Furthermore,`the percent of CO indicated by IIC is less rthan SC. Consequently, by idling an engine with 1/2 of the cylinders firing and 1/2 of the cylinders pumping unrestricted air, it is possible to reduce the percent 'of CO and hydrocarbons to acceptable values as set by the existing laws, e.g. Los Angeles, on automotive exhaust pollution control and to reduce the weight of pollutant exhausted per hour VWUZ IIE and Wl/ZXIIC below the corresponding values WAXSE and WAXSC of an engine firing at all cylinders and having the allowed percent of hydrocarbons SE and carbon monoxide SC.

The engine operation with l/z of the cylinders may be continued until the remaining cylinders must be activated to achieve power in excess of that generatable with split engine operation.

Referring now to FIGURE 3 of the drawings, a description will be undertaken of an engine charge forming system which permit increased fuel economy as well as contributing to a substantial reduction of unburned hydrocarbons and CO. In this case, an engine is shown generally at 40 and includes active cylinders 42 having pis tons 44 slidably disposed therein and inactivecylinders 46 having pistons 4S slidably disposed therein. It is to be u'nderstood'thatallv cylinders are -operative to produce power under normal and high power operating conditions and that the right hand or inactive cylinders 46 are inoperative only'under `coasting or near idling conditions. All of the cylinders include intake and exhaust valves 50, 52 and 54, 56 as well vas spark plugs' 58 and 60. Each active cylinder 42 includes an induction passage 62 and a common carburetor device 64 associated therewith, Deyice 64 includes a throttle valve`66 for'controlling the quantity of combustible mixture flow through passage 62. Throttle 66 is articulated through lever 68 and link 70'to an accelerator pedal 72. A conventional accelerator pump 76 is also adapted to be operated by pedal -72 through link and levers 73`and S0. Y

Exhaust gas from cylinder 42 is discharged through passage 74.

Each inactive cylinder 46 includes an induction passage 82 ow through which-is controlledby a throttle valve 84 of'a carbureting device indicated generally at '36. The inactive cylinders are exhausted through a passage 88 which'is adapted to communicate with' active cylinder" exhaust Ypassage 74 through a bypass passage `90.

Under normal or high power operating conditions, all cylinders are operative to supply power'to the common crankshaft 92 to which the pistons 44 and 48 are artcu lated through rods 94 and 96 respectively.

The mechanismwill now be described which permits split engine operation, eig. half cylinders ltiring with the other half merely pumping air. It wasV earlier pointed out that during deceleration, the fuel-air ratio may be too rich to burn in the cylinders or Vmay be contaminated with too much residual exhaust to support combustion. In the case of a too rich combustible mixture, by ,bleeding air exhausted by the pumping or inactive cylinders 46 into the exhaust system of the firing cylinders, a combustible mixture is achieved. For this purpose, air from pumping cylinders 46 passes through the hot exhaust manifold 8S which includes a heat storing device 98. Thus the air is preheated prior to flowing through bypass 99 and mixing with the partially burned exhaust gas from passage SS in exhaust combustion space 19d.

Immediately after deceleration is initiated by closing the throttle, the intake manifold walls are covered with liquid fuel which normally is simply pumped to the atmosphere without being burned. In the' present system, this residual fuel is mixed with air from passage 95 and the combustible mixture in space llil is ignited by a spark plug M32 which is adapted to be energized by distributor lil@ through a switch member l which interrupts current to the inactive spark plugs 6i) when the vehicle is coasting. Thus distributor ltld will cause spark plug 162 to re periodically and ignite the combustible mixture in space lith consuming the heretofore unburned combustibles.

After the mixture in the manifold returns to normal, because of the elimination of excess fuel, only a limited amount of oxidation of exhaust may be required and this may be achieved by the incoming air from bypass 96.

Since only one-half of the cylinders are operative under coasting or idling conditions, the resulting manifold depression during deceleration can be kept low enough (high enough absolute pressure) to permit complete combustion or suciently good combustion to take place Without generation of excessive power that would interfere with car braking. This condition is not practical on engines tiring on all cylinders during deceleration since keeping manifold depression high enough to insure combustion results in the generation of Sumcient engine power to seriously interfere with car barking.

In order to maintain the inactive cylinders in a nonpower producing condition and also to prevent fuel from being drawn therethrough, a unique throttle and air flow control system has been devised. As seen in FIGURE 3, a second induction or air bypass passage lll is provided and is adapted to receive air from the air cleaner and discharge the same into induction passage 82 posteriorly of throttle valve S6. Flow through bypass passage TGS is controlled by a throttle valve llt) which is either fully opened or closed depending on whether the engine is idling (or coasting) as opposed to operating under normal or high power engine operation.

Assuming a normally carbureted engine, the portion of the engine pumping air is the right hand side, as viewed in FIGURE 3, in which case carburetor throttle 84 is closed and air bypass throttle 115B is open.

After throttle 6d of the active cylinders 42 has opened to a predetermined amount, or after the engine has achieved a given manifold depression, and the driver depresses accelerator pedal 72 further, the following events are made to occur in the following order: (l) bypass SW3 is closed by closing throttle 1li), (2) accelerating pump M2 squirts fuel above closed throttle Se', and (3) throttle 34 opens in proportion to the position of the accelerator pedal but not in excess of the amount which will permit the fuel-air mixture at the intake valve to be combustible.

The above sequence is explained as follows. For a given manifold depression, the mass air flow through an induction passage is approximately equal to air density times volumetric efficiency times engine angular speed almost at the instant the throttle opens. Being heavier, the fuel acquires velocities much lower than the air, thus some engine revolutions may take place during throttle opening, or immediately afterwards, in which the air does not carry adequate fuel for combustion in the cylinders. Consequently, it is necessary that the accelerating pump delivers the fuel before the air is admitted into the manifold so that the slower traveling fuel may reach intake d valve 52 and enter the cylinder at the time the corresponding quantity of air reaches this point.

This symchronization of fuel and air flow can be facilitated if the fuel from the accelerating pump is dumped, for example, upon throttle valve 34 at the lower edge thereof during the initial opening and immediately after closing the bypass air valve or throttle 110.

The large pressure differential between the atmospheric condition ahead of throttle 84 and manifold depression past it Will atomize and impart very high velocity to the fuel droplets thus facilitating its movement by the incoming air. This phenomenon may be further enhanced by designing a streamlined manifold thus reducing the condensation of fuel upon the manifold walls.

T he mechanism for interrelating the actuation of Vthrottle 345 and bypass throttle lli) Will now be considered in detail. VA throttle link H4 is articulated at 116 to active throttle control link 7?. The other end of link llldis connected through a lost motion connection i118 to accelerating pump actuating lever 31.29. Accelerating pump lever l2@ also includes a movable contact element 22 of a switch E24 which controls the flow of current from source 126 to a solenoid i233 which, in turn, controls the movement of an armature 130. Armature 13d is articulated through a link 132 to bypass throttle Mtl. When solenoid ld is :ie-energized, spring i3d maintains bypass throttle lli@ in a wide open position as shown in FIG- URE 3.

As accelerator pedal '72 is moved from its idle position 13o to the full line position shown, only the left hand or active throttle do opens since lost motion connection 118 precludes any actuation of throttle llt) until the slot 15S has moved to its leftmost position. Further opening movement of accelerator pedal 72 will initiate movement of accelerator pump lever l2@ thus closing switch T24, energizing solenoid T28 and moving bypass throttle llt) to a fully closed position. It is important that the closing of bypass valve-orV throttle ltl and the stopping of bypass air flow around carburetor do take place substantially before `accelerating pump lli delivers its fuel.

Still further opening movement of accelerator pedal 72 from the full line position to lfttl will continue to open activeV throttle 65 and actuate its accelerating pump 76. This movement also actuates accelerator pump 112 which delivers fuel on top of throttle This fuel will be drawn past the edge of the throttle into the local high speed air stream between the throttle edge and induction passage wall. This fuel is allowed to travel almost to intake valve 52 before throttle Se is opened.

The delayed air flow is achieved as follows. While the movement of accelerator pedal '72 is actuating pump M2 through lever E22, the upper'end of this lever cornpresses a preloaded spring 144- which biases against throttle lever 146. Throttle lever 146 and pump lever 124) are thus relatively movable and the former isV connected through a rod 148 to a dashpot device 115i). Opening movement of lever 1Z0 is resiliently transmitted to lever 146 through spring M4. Thus the dashpot 150 and spring 144 combined to retard opening of throttle 84and, hence, causing a retardation of air llow past throttle 34 substantially equivalent to the time required by the fuel to reach the intake valve. Y

Adjustment of the Vforce of spring 144 and, therefore, the opening of throttle 34 may be varied through an adjustable stop screw 145.

Thus it will be seen the present invention uniquely provides means operative during coasting conditions to first consume or burn combustible materials extant in .the

manifold after which the engine is made to function in a manner in which unburned hydrocarbons and CO are maintained at a level compatible with good fuel economy as Well as with reasonable standards of health.

While the system as thus far describedresults in conanonyme U satisfy the laws in those states having passed upon this matter, a further modification of the basic system results in still further improvements in this emission condition. Reference is now made to FIGURE and the graph shown in FIGURE 4 the latter which shows the added improvements achieved by this modification.

The basic system of FIGURE 5 is the same as that of FIGURE 3, therefore, only the lower half of the system is shown inFIGURE 5 to represent the instant modication. In all other respects like numerals are used to represent the same elements as shown in FIGURE 3 and it is to be understood that the remainder of the system is identical therewith.

In the earlier modification of FIGURE 3, an additional air bypass passage is added to the exhaust system in order to convey heated air from the inactive cylinders to exhaust chamber for combustion with the exhaust gases issuing from the active cylinders 42. With this arrangement, it is necessary to insulate air bypass passage 90 and, notwithstanding this precaution, considerable heat losses are experienced in the transmission of the air to chamber 100. As a consequence, the combustion which takes place in chamber 100 is less complete than desired since the air supplied to the exhaust gases is at a lower temperature, e.g. 900 F., than is now found to be possible with the modification of FIGURE 5.

In the modification of FIGURE 5, instead of adding a separate air bypass passage to connect the two exhaust systems, as is done in the earlier modification, the normal and otherwise available exhaust cross-over passage is utilized to house the means for conveying of air to further oxidize the exhaust gases from the active cylinders 42. In the normal engine of the type in which the subject system is to be employed, the exhaust gases from one bank of cylinders 42 are conveyed through exhaust cross-over passage 150 to a common exhaust pipe 152 which is also fed by the other cylinder bank. Since this exhaust cross-over passage is already available, no additional structure is provided up to this point. Instead, a relatively small, heat resistant tube 154, e.g. stainless steel, is mounted within exhaust cross-over passage 150 and includes one end 156 which extends upwardly within exhaust passage 88 of the inactive cylinders and terminates at the other end 158 proximate spark plug 102 disposed at the juncture of exhaust passage 74 from the active cylinders and cross-over passage 150.

As a result of this arrangement, when split engine operation is occurring and the inactive cylinders are merely pumping air, the hot exhaust gases from the active cylinders are flowing through exhaust cross-over passage 150 to common exhaust pipe 152. At the same time, a limited quantity of air from the inactive cylinders 46 is counterflowing through pipe or tube 154. This air is thereby being progressively preheated by the exhaust gases until it is discharged at the hottest end of the cross-over passage proximate spark plug 102.

In this way, the preheated air is mixed with the exhaust gases at a considerably higher temperature, e.g. 1200 F., than in the first modification and as a result more efficient combustion takes place and the quantity of CO and unburned hydrocarbons is still further reduced to the levels indicated on the dash curves of FIGURE 4. It Vwill now be seen, in referring to FIGURE 4, that with one-half of the engines cylinders working, the unburned hydrocarbons now being emitted are represented by `IIE' and the CO by IIC'. The added improvement in the emission ofV unburned combustibles isV readily apparent from the graph and both the COand unburned hydrocarbons are now well below the values SC and SE typically required by statute.

The arrangement of tube 154 within exhaust cross-over passage 150 results in a counter-dow situationV in which the air is flowing in the opposite direction to the exhaust gases in such a way that the air is discharged into the afterburning combustion zone at essentially the highest temperature possible.

To be sure of an adequate flow of fresh or afterburner air through pipe 154, an air flow responsive or unbalanced valve 160 is mounted in exhaust passage 88 of the inactive cylinders 45. Valve 160 is biased in a closing direction through a spring member 162. Valve .160 is suitably slotted to permit pipe 154 to extend therethrough and to terminate immediately anteriorly of the closed valve. Spring 12 is calibrated in such a way that when all of the cylinders are operative to supply power, the flow of exhaust gas through passage d8 will create a suticient pressure drop across the valve to maintain the same in an open condition against the force of the spring. However, during idling or coasting conditions flow through passage SS is insufficient to overcome spring 162, consequently, valve 160 will be maintained closed. By thus closing passage 8S sufficient air pressure is maintained anteriorly thereof to insure adequate air flow through pipe 154.

Spark plug 102 is energized in the same manner as already described'with respect to the modification of FIGURE 3 and will ignite the unburned combustibles flowing from passage '74 when combined with the relatively fresh high temperature air issuing from pipe 154.

It is apparent that various modifications may be made in the illustrated embodiments of the present invention within the intended scope of the invention as set forth in the hereinafter appended claims.

I claim:

1. A charge forming device for an internal combustion engine comprising a first group of cylinders and a second group of cylinders, induction passage means communicating with said first group of cylinders, first carburetor means coacting with said induction passage for providing a combustible mixture to said first group of cylinders, said first carburetor means including a throttle valve, an accelerator pedal, linkage means for articulating said accelerator pedal and throttle valve, a second induction passage communicating with said second group of cylinders, second carburetor means coacting with said second induction passage for supplying a combustible mixture to said second group of cylinders, a throttle valve for controlling the quantity of flow through said second inr duction passage means, a second linkage device for operatively connecting said accelerator pedal and said second throttle', said second linkage device including a lost motion arrangement whereby initial Opening movement of said accelerator pedal will open said first throttle while the second throttle remains closed, an air passage connected in parallel to a portion of said second induction passage and adapted to bypass air around said second throttle, a third throttle valve in said bypass passage, said third throttle valve normally biased in an open position to permit air flow through said bypass passage when said second throttle is closed, means responsive to the opening movement of said second linkageV device for closing said third throttle just prior to opening of said second throttle, means for providing an electric spark to all of said cylinders, and means operable when said third throttle is in its open position to interrupt the fiow of current to the spark providing means associated with said second group of cylinders.

2. A charge forming device as set forth in claim 1 in which said second carburetor means includes an accelerator pump, said pump. being operable by the lost motion arrangement to admit fuel to the second induction passage immediately anterior of the associated throttle just prior to the opening of the latter.

3. A charge forming device as set forth in claim 1 in which said second linkage device includes first and second lever members, said first lever being connected to the accelerator pedal through the lost motion arrangement, and a spring member for resiliently connecting said rst and second lever members, said second lever being directly connected to said second throttle.

4. A charge forming device as set forth in claim 3 which includes a dashpot device, said lsecond lever also being connected to said dashpot device to delay the opening movement of said second throttle after said first lever is actuated.

5. A charge forming device as set forth in claim 3 which includes a solenoid device operable when energized to close said third throttle, a switch including a movable contact fixed to said first lever, said contact being adapted to close said switch and energize the solenoid during the initial movement of said rst lever whereby the third throttle will be closed prior to the opening of the second throttle.

6. A charge forming device as set forth in claim 3 which includes means for injecting a limited quantity of fuel into the second induction passage during the interval between the closing of the third and opening of the second throttles.

7. A charge forming device as set forth in claim 6 in which the fuel injecting means comprises a pump adapted to discharge into the second induction passage immediately anterior to the lower edge of the second throttle.

8. A charge forming device for an internal combustion engine including a first group of cylinders, a second group of cylinders, each of said cylinders including a piston member -slidably disposed therein and articulated through a rod element to a common crankshaft, a first carburetion system for supplying a combustible mixture to said first group of cylinders, a second carburetion system for supplying a combustible mixture to said second group of cylinders, each of said carburetion systems including a throttle valve for controlling the quantity of combustible mixture flow therethrough, a common accelerator pedal suitably articulated to each of said throttle valves, a lost motion device, said accelerator pedal being articulated to said second carburetion system throttle through said lost motion device such that initial opening movement of said pedal will impart an opening movement only to said rst system throttle while the second system throttle remains in a closed position, an air passage for bypassing air around said second system throttle, a valve member in said bypass passage permitting air to flow through said bypass passage when said second system throttle is closed and to block air flow through said passage when said second system throttle is about to open, means for providing an electric spark to all of said cylinders to ignite the combustible charge therein, means for interrupting the spark to the second group of cylinders when said bypass passage valve is open and said second system throttle is closed whereby the power output from the engine is maintained by said first group of cylinders while said inactive cylinders merely pump air, passage means associated with said first group of cylinders and adapted to discharge the exhaust gases therefrom to a chamber, a second air bypass passage communicating said second group of cylinders with said chamber whereby fuel free air is lsupplied to the exhaust gases from said iirst group of cylinders to oxidize unburned combustibles contained therein.

9. A charge forming device as set forth in claim 8 which includes an electric spark device disposed in said exhaust gas chamber, said spark device being operative to ignite the combustibles in said chamber only when the spark is interrupted to the second group of cylinders.

10. A charge forming device as set forth in claim 9 which includes an exhaust cross-over passage leading from said chamber to a common exhaust passage, said second air bypass passage comprising a pipe disposed within the cross-over passage, said pipe including one end terminating proximate the spark device disposed in said exhaust gas chamber for providing preheated air to facilitate further combustion of said exhaust gases.

11. A charge forming device as set forth in claim 10 which includes valve means disposed in said second air bypass passage, said pipe including another end in said second air bypass passage terminating immediately anteriorly of said valve means, said valve means being adapted to close when said second system throttle is closed to insure adequate air fiow through said pipe.

12. A charge forming device as set forth in claim 11 in which said valve means includes an unbalanced valve member, a spring element biasing said valve member in a closed position, said valve member being adapted to open against the force of the spring element when the pressure drop across the member exceeds a predetermined value.

13. A split engine rsystem of the type including a first carburetion device for supplying a combustible mixture to one-half the engine cylinders under all engine operating conditions and a second carburetion device for supplying a combustible mixture to the other half of the cylinders under normal or high power operating conditions, said second carburetion device being inoperative to supply a combustible mixture under coasting or idling conditions, in which an air passage is adapted to bypass air around the second carburetion device and to supply such air to said other half of the cylinders when the latter device is rendered inoperative to supply a combustible mixture, a common exhaust passage for receiving the exhaust gases from all of the engine cylinders, an exhaust crossover passage for conveying the exhaust gases from the continuously operating cylinders to the common exhaust passage, a pipe disposed within said cross-over passage and communicating at one end with the air bypass passage, the other end of said pipe terminating proximate the inlet of the cross-over passage permitting air preheated substantially to the temperature of the exhaust gas entering the cross-over passage to mix with and oxidize a large portion of the unburned combustibles contained in said exhaust gas.

14. A split engine system as set forth in claim 13 in which valve means is provided in the air bypass passage immediately posteriorly of said one end of said pipe, said valve means closing under said coasting or idling conditions to insure adequate air ow through said pipe.

References Cited by the Examiner UNITED STATES PATENTS 1,956,657 5/ 34 Scheel.

2,0818 18 7/ 37 Messinger.

2,114,655 4/38 Leibing.

2,420,925 5 47 Wirth 123--127 2,937,490 5 60 Calvert 60-30 JULUS E. WEST. Primary Examinez'. 

13. A SPLIT ENGINE SYSTEM OF THE TYPE INCLUDING A FIRST CARBURETION DEVIDE FOR SUPPLYING A COMBUSTIBLE MIXTURE TO ONE-HALF THE ENGINE CYLINDERS UNDER ALL ENGINE OPERATING CONDITIONS AND A SECOND CARBURETION DEVICE FOR SUPPLYING A COMBUSTIBLE MIXTURE TO THE OTHER HALF OF THE CYLINDERS UNDER NORMAL OR HIGH POWER OPERATING CONDITIONS, SAID SECOND CARBURETION DEVICE BEING INOPERATIVE TO SUPPLY A COMBUSTIBLE MIXTURE UNDER COASTING OR IDLING CONDITIONS, IN WHICH AN AIR PASSAGE IS ADAPTED TO BYPASS AIR AROUND THE SECOND CARBURETION DEVICE AND TO SUPPLY SUCH AIR TO SAID OTHER HALF OF THE CYLINDERS WHEN THE LATTER DEVICE IS RENDERED INOPERATIVE TO SUPPLY A COMBUSTIBLE MIXTURE, OF COMMON EXHAUST PASSAGE FOR RECEIVING THE EXHAUST GASES FROM ALL OF THE ENGINE CYLINDERS, AN EXHAUST CROSSOVER PASSAGE FOR CONVEYING THE EXHAUST GASES FROM THE 